1. Field of the Invention
The present invention relates to a process for preparing aminofunctional organoalkoxysilanes by reacting chlorofunctional organoalkoxysilanes with ammonia or an organic amine, separating the ammonium chloride or organic amine hydrochloride by-product formed, and working-up the resulting crude product by distillation. Aminofunctional organoalkoxysilanes will hereinafter also be referred to as aminosilanes.
2. Description of the Background
Aminosilanes have a wide range of uses. They are employed, for example, for the sizing of glass fibers and are employed as processing aids in the foundry industry. They likewise serve as adhesion promoters for storage-stable resins.
It is known that aminofunctional organoalkoxysilanes can be prepared from chlorofunctional organoalkoxysilanes and ammonia or organic amines (DE-C 10 23 462, DE-C 27 49 316, DE-C 27 53 124, German patent application 100 58 620.1).
When aminofunctional organoalkoxysilanes are heated, an alkoxy group on the silicon atom is eliminated to form the alcohol corresponding to the alkoxy group together with a cyclic compound containing the Sixe2x80x94N structural element, for example: 
As a consequence, distillation of an aminofunctional organoalkoxysilane results in a decrease in the content of the linear aminofunctional organoalkoxysilane and a simultaneous increase in the abovementioned cyclic compound. This is a disadvantage because the desired high content of linear aminofunctional organoalkoxysilane, as is necessary, for example, for applications of the aminofunctional organoalkoxysilane in sizes in glass fiber production, is no longer achieved.
Accordingly, one object of the present invention is to provide a way of reducing the content of cyclic compounds in aminofunctional organoalkoxysilanes.
Briefly, this object and other objects of the present invention as hereinafter will become more readily apparent can be attained by a process for preparing an aminofunctional organoalkoxysilane of formula I
R2Nxe2x80x94(CH2)yxe2x80x94Si(OR1)3xe2x88x92nR2nxe2x80x83xe2x80x83(I),
wherein the R groups bonded to nitrogen are identical or different and each individual R group is hydrogen, an alkyl radical having from 1 to 4 carbon atoms, an aryl radical or an arylalkyl radical,
R1 is an alkyl radical having from 1 to 8 carbon atoms or an aryl radical,
R2 is an alkyl radical having from 1 to 8 carbon atoms or an aryl radical,
y is 2, 3 or 4 and n is 0, 1 or 2, comprising:
reacting a chlorofunctional organoalkoxysilane of formula II
Clxe2x80x94(CH2)yxe2x80x94Si(OR1)3xe2x88x92nR2nxe2x80x83xe2x80x83(II),
wherein R1, R2, y and n are as defined above, with ammonia or an organic amine of formula III
HNR2xe2x80x83xe2x80x83(III),
wherein the two R groups are identical or different and each is defined as described above;
separating organic amine hydrochloride or ammonium chloride by-product which is formed in the reaction;
distilling the resulting crude product, thereby preparing an aminofunctional organoalkoxysilane or the product fraction of an aminofunctional organoalkoxysilane; and
treating the aminofunctional organoalkoxysilane or the product fraction of an aminofunctional organoalkoxysilane with an alcohol.